Calprotectin Independently Predicts Relapse in Treated RA

Calprotectin is a biomarker of disease activity in rheumatoid arthritis (RA) and psoriatic arthritis (PsA) and predicts relapse in juvenile idiopathic arthritis. Higher drug trough serum levels are associated with a good response in patients treated with tumor necrosis factor inhibitors (TNFi).

Biological therapies have dramatically improved the management and prognosis of rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Remission or low disease activity is possible in an increasing number of patients. Nevertheless, persistent remission is more difficult to achieve since disease relapses are common.

Scientists from the University of Barcelona (Barcelona, Spain) carried out a longitudinal, prospective, one-year single-center study of 103 patients (47 RA, 56 PsA) receiving TNFi in remission or with low disease activity. All patients underwent clinical assessment at baseline and at 4, 8, and 12 months, including 28-joint swollen and tender joint counts (28-SJC and 28-TJC, respectively), physician and patient global assessment with visual analogue scales (0–100 mm), erythrocyte sedimentation rate (ESR; mm), and C-reactive protein (CRP; mg/dL).

Calprotectin serum levels, TNFi trough serum levels, and antidrug antibodies were determined at baseline (visit 0) and during disease relapse using an enzyme-linked immunosorbent assay (ELISA) test kit Calprolab, calprotectin ELISA (ALP), and Promonitor, respectively. To reduce variations in calprotectin determinations, the whole procedure was performed in a Triturus autoanalyzer. Additionally, serum samples were collected at 4, 8, and 12 months of follow-up to assess longitudinal changes in drug trough serum levels.

The scientists reported that 95 patients completed one year of follow-up, of whom 12 experienced a relapse. At baseline, relapsers had higher calprotectin levels, lower TNFi TSL, and higher power Doppler (PD) activity than nonrelapsers. Receiver operating characteristic (ROC) analysis showed calprotectin fully predicted relapse (area under the curve (AUC) = 1.00). The cut-off levels determined by ROC analysis for the optimal prediction of relapse for calprotectin, TNFi serum levels, and PD score were 3.7 μg/mL, 1.61 μg/mL, and 4, respectively.

The authors concluded that time-to-remission/low disease activity, calprotectin serum levels, TNFi TSL, and PD score were significantly associated with disease relapse. However, only baseline calprotectin serum levels independently predicted disease relapse in RA and PsA patients under TNFi therapy. The study was published on December 13, 2018 in the journal Arthritis Research and Therapy.

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